Sensei,San,Chan,Kun
 

i think it would be riku-san,

but i wouldn't really know

you need the language section

You should ask this in the Japanese Language Help Forum.

Jaydelart is right. I doubt if you will get good answers in General Discussion. People will be answering saying "I think...", "I heard that.." , etc.

Believe me, this question is much more complex than you have probably thought. There are many exceptions as well as general rules. Those who don't speak Japanese fluently or who have never attended school in Japan will not be able to answer this.

I will gladly give my answer in the Language section.

EDIT: Oh...here it is.

In general, teachers address boys by their last name and "-kun".

teachers usually call students by their last name and i think they'd use san. sempai is for any upperclassmen or anyone in a grader higher than your own basically. chan is more feminine or for children, like a cutesy way of calling someone i guess. ppl usually use this for close friends too. hope this helps. sorry if i'm incorrect

By teachers:

Boys: Last name+kun

Girls: Last name+san

In terms of how students refer to each other, it is all over the map.

hmm, depends on what age you are, what kind of teacher you have. my teachers called me -san, but i only got japanese in university level.

some of my japanese friends call me chan, but not that often. mostly they leave away everything.

I think ~kun ends in high school. However you can can hear bosses use it for their younger staff. Even to women, sometimes.